Conventional lighting systems employing, for example, LEDs, tungsten bulbs, or halogen strip lights, require electrical current to be carried in close proximity to where illumination is to be provided. In addition, some conventional lighting elements, for example tungsten bulb filaments, reach extremely high temperatures during operation. For everyday applications the presence of electrical current and high temperatures does not present a significant problem. However, this could be highly dangerous when used in hazardous and potentially explosive environments, for example during a gas leak at an offshore platform, a petrochemical plant, a mine, an oil taker or a distillery.
For some hazardous environments, a series of LED point lights can be installed to provide an escape guide path for use in an emergency. However, each LED light section has to be individually installed and each electrical connection must be regularly inspected and maintained to ensure the safety of the system, which leads to high costs. In addition, for some extremely hazardous environments, it is not possible to install any form of conventional emergency lighting because the supply of even tiny amounts of electrical current would be too dangerous.
WO 98/45645 discloses a method and apparatus for providing illumination based on a laser light source and a side emitting fiber optic cable. The laser light source emits a beam of light that is coupled into the side emitting fiber optic cable. The beam of light then propagates along the fiber optic cable and light is gradually emitted through the sides of the fiber optic cable. The application details how the apparatus could be used in an emergency lighting application as it can provide a continuous path of light that contains no electrical power. However, if the fiber optic cable is fractured or severed during operation, and particulates such as coal dust gather on the fractured or severed portion and absorb light energy, then the result can be a rapid and dangerous rise in temperature. In the presence of a low temperature ignition gas, such as diethyl ether, the result of such a temperature rise can literally be explosive. The solution described in WO 98/45645 is for the system to shut down or shutter the light source if the cable is cut or damaged. However, emergency lighting systems are the last resort for aiding escape from a building/facility in an emergency. Therefore, the fact that this system may shut down in an emergency situation renders it useless.